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Top 150 Coding Exercises

Master the most important algorithms and data structures through 150 carefully curated exercises across 10 categories — from beginner to advanced.

Categories

Difficulty

Showing 150 exercises

hash-maparraytwo-pointer

Best Time to Buy and Sell Stock📦

greedyarraysliding-window

Contains Duplicate📦

Product of Array Except Self📦

prefix-sumarray

Maximum Subarray (Kadane's)📦

dynamic-programminggreedykadane

two-pointersortingarray

Container With Most Water📦

two-pointergreedy

Rotate Array📦

arrayin-placereverse

Find Minimum in Rotated Sorted Array📦

binary-searcharray

Merge Intervals📦

sortingarrayintervals

Valid Anagram🔤

hash-mapstringsorting

Longest Substring Without Repeating Characters🔤

sliding-windowhash-setstring

Valid Palindrome🔤

two-pointerstring

Group Anagrams🔤

hash-mapstringsorting

Longest Common Prefix🔤

Reverse Words in a String🔤

stringtwo-pointer

String to Integer (atoi)🔤

Count and Say🔤

stringsimulation

Minimum Window Substring🔤

sliding-windowhash-mapstring

Decode Ways🔤

dynamic-programmingstring

Reverse Linked List🔗

linked-listtwo-pointerrecursion

Detect Cycle in Linked List🔗

linked-listtwo-pointerfloyd

Merge Two Sorted Lists🔗

linked-listrecursion

Remove Nth Node From End🔗

linked-listtwo-pointer

Reorder List🔗

linked-listtwo-pointer

linked-listhash-mapdesign

Palindrome Linked List🔗

linked-listtwo-pointer

Intersection of Two Linked Lists🔗

linked-listtwo-pointer

linked-listmerge-sortdivide-conquer

Copy List with Random Pointer🔗

linked-listhash-map

Maximum Depth of Binary Tree🌳

treedfsrecursion

Invert Binary Tree🌳

Validate Binary Search Tree🌳

Level Order Traversal (BFS)🌳

Lowest Common Ancestor🌳

treebstrecursion

Binary Tree Right Side View🌳

Construct BST from Preorder🌳

treebstdivide-conquer

Path Sum II🌳

treedfsbacktracking

Serialize and Deserialize Binary Tree🌳

Kth Smallest in BST🌳

Number of Islands🕸️

Clone Graph🕸️

Course Schedule (Topological Sort)🕸️

graphtopological-sortdfs

Pacific Atlantic Water Flow🕸️

Dijkstra's Shortest Path🕸️

graphdijkstrashortest-path

Word Ladder🕸️

Alien Dictionary🕸️

graphtopological-sortstring

Graph Valid Tree🕸️

graphunion-finddfs

Rotting Oranges (Multi-source BFS)🕸️

Walls and Gates🕸️

Climbing Stairs🧩

dynamic-programmingfibonaccimemoization

Coin Change🧩

dynamic-programmingbfs

Longest Increasing Subsequence🧩

dynamic-programmingbinary-search

0/1 Knapsack🧩

dynamic-programmingknapsack

Longest Common Subsequence🧩

dynamic-programmingstring

Edit Distance🧩

dynamic-programmingstring

dynamic-programmingstringtrie

Unique Paths🧩

dynamic-programmingmath

Jump Game II🧩

dynamic-programminggreedy

Burst Balloons🧩

dynamic-programminginterval-dp

Search in Rotated Sorted Array🔍

binary-searcharray

Kth Largest Element🔍

heapsortingquickselect

Top K Frequent Elements🔍

heaphash-mapbucket-sort

Sort Colors (Dutch National Flag)🔍

sortingtwo-pointerin-place

Median of Two Sorted Arrays🔍

binary-searchdivide-conquer

Find Peak Element🔍

binary-searchdivide-conquer

Merge K Sorted Lists🔍

heaplinked-listdivide-conquer

Count of Smaller Numbers After Self🔍

merge-sortbinary-indexed-treedivide-conquer

sortingbinary-search

Wiggle Sort II🔍

Reverse Integer🔢

Palindrome Number🔢

Power Function (Fast Exponentiation)🔢

mathdivide-conquerrecursion

Sqrt(x) — Integer Square Root🔢

binary-searchmath

Count Primes🔢

Roman to Integer🔢

mathstringhash-map

Happy Number🔢

mathhash-setfloyd

Excel Sheet Column Number🔢

Fraction to Recurring Decimal🔢

mathhash-mapsimulation

Largest Number🔢

sortingmathstring

Single Number⚡

bit-manipulationxor

Number of 1 Bits (Hamming Weight)⚡

bit-manipulation

Reverse Bits⚡

bit-manipulation

Missing Number⚡

bit-manipulationmathxor

Counting Bits⚡

bit-manipulationdynamic-programming

Power of Two⚡

bit-manipulation

Sum of Two Integers Without +/-⚡

bit-manipulationxor

Bitwise AND of Numbers Range⚡

bit-manipulation

Find the Duplicate Number⚡

bit-manipulationfloydarray

XOR Queries of a Subarray⚡

bit-manipulationprefix-sumxor

Valid Parentheses📚

Implement Queue Using Stacks📚

stackqueuedesign

Daily Temperatures📚

stackmonotonic-stack

Largest Rectangle in Histogram📚

stackmonotonic-stack

Evaluate Reverse Polish Notation📚

Sliding Window Maximum📚

stackqueuedeque

Implement Stack Using Queues📚

stackqueuedesign

Next Greater Element📚

stackmonotonic-stackarray

Trapping Rain Water📚

stacktwo-pointerarray

Sum of Digits🔢

Reverse a String🔤

stringtwo-pointer

Count Vowels🔤

Find Maximum in Array📦

Check if Array is Sorted📦

Remove Duplicates from Array📦

Flatten Nested Array (1 level)📦

First Non-Repeating Character🔤

Capitalize First Letter of Each Word🔤

Count Words in a String🔤

Find All Pairs with Given Sum📦

Celsius to Fahrenheit Converter🔢

Check Balanced Brackets📚

GCD and LCM🔢

Check Prime Number🔢

Anagram Check🔤

stringsortinghash-map

Intersection of Two Arrays📦

Pascal's Triangle Row🔢

mathdynamic-programming

Move Zeros to End📦

arraytwo-pointerin-place

Implement strStr (Find Substring)🔤

stringsliding-window

Subarray Sum Equals K📦

arrayprefix-sumhash-map

Spiral Matrix📦

arraymatrixsimulation

Longest Palindromic Substring🔤

stringdynamic-programmingtwo-pointer

Find All Anagrams in a String🔤

stringsliding-windowhash-map

Number of Connected Components🕸️

graphunion-finddfs

Decode String📚

stackstringrecursion

Maximum Product Subarray📦

arraydynamic-programming

Longest Consecutive Sequence📦

Task Scheduler🔢

mathgreedyhash-map

Insert Interval📦

arrayintervalssorting

Minimum Size Subarray Sum📦

arraysliding-windowtwo-pointer

Flatten Binary Tree to Linked List🌳

treedfslinked-list

Combination Sum📦

arraybacktrackingrecursion

Permutations📦

arraybacktrackingrecursion

Letter Combinations of a Phone Number🔤

stringbacktrackingrecursion

arraybacktrackingbit-manipulation

Gas Station📦

Partition Equal Subset Sum🧩

dynamic-programmingarray

Minimum Path Sum in Grid🧩

dynamic-programmingmatrix

Regular Expression Matching🧩

dynamic-programmingstringrecursion

Wildcard Matching🧩

dynamic-programmingstring

Longest Valid Parentheses📚

stackstringdynamic-programming

Jump Game III🕸️

Maximal Rectangle📚

stackmatrixdynamic-programming

Palindrome Partitioning🧩

dynamic-programmingbacktrackingstring

N-Queens Problem📦

backtrackingarray

Sudoku Solver📦

backtrackingarraymatrix

Minimum Window to Sort Array🔍

sorting-searchingarray

Shortest Path in Binary Matrix🕸️